Doc 20 §6 D1, first slice: wasm/sched/context.{h,cpp} implements
create / yield_park / mark_ready / drain with the registry as truth.
The shape that matters — a STAR, not libcontext's symmetric swap:
contexts only ever swap OUT to the scheduler, and only the scheduler
swaps IN. So "is this target safe to enter?" stops being a guess
(libcontext's swap_suspended / parked / hot-main refusals) and becomes a
lookup: the registry says Parked/Ready and holds the buffer. Doc 19's
refused-resume is unrepresentable here because resume is not a decision
made at the swap site.
Enforced, not hoped for:
- at most one transition in flight (drain() refuses re-entry, so a
context calling drain() cannot turn the star into a cycle);
- mark_ready() never resumes inline — it queues, and drain() resumes
from a clean stack (doc 13 §1.4's deferred-wake law, per context);
- yield_park() off a context is REFUSED, which is the "nothing parks in
place" rule made mechanical;
- destroy() on a non-Finished context is refused (freeing a parked
stack strands whatever is on it);
- FIFO ready queue (no starvation);
- main-thread-only, per doc 21 §2's pthread finding.
Memory is accounted from the start (doc 20 risk 1): live/peak contexts,
bytes/peak bytes, and per-context asyncify high-water measured from
asyncify_data.stack_ptr — the same quantity the shim reports as `rem=`,
from the other end. Sizes deliberately start at 128 KB C stack + 128 KB
asyncify buffer rather than inheriting libcontext's 512 K, so the number
gets derived from evidence; a >75% buffer use beacons BUFFER-PRESSURE
because that overflow is silent corruption, not a crash.
No production path runs on this yet — dispatch moves at D2.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TEHGiiXMShNXbBr7gSJ7iz
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